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LibJS: Stop converting between Object <-> IteratorRecord all the time

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This patch makes IteratorRecord an Object. Although it's not exposed to
author code, this does allow us to store it in a VM register.

Now that we can store it in a VM register, we don't need to convert it
back and forth between IteratorRecord and Object when accessing it from
bytecode.

The big win here is avoiding 3 [[Get]] accesses on every iteration step
of for..of loops. There are also a bunch of smaller efficiencies gained.

20% speed-up on this microbenchmark:

    function go(a) {
        for (const p of a) {
        }
    }
    const a = [];
    a.length = 1_000_000;
    go(a);
This commit is contained in:
Andreas Kling 2023-12-07 10:44:41 +01:00
parent 4966c083df
commit 4699c81fc1
23 changed files with 226 additions and 144 deletions
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6
Userland/Libraries/LibJS/Runtime/AsyncFromSyncIterator.h
View file

@ -18,7 +18,7 @@ class AsyncFromSyncIterator final : public Object {
JS_DECLARE_ALLOCATOR(AsyncFromSyncIterator);
public:
static NonnullGCPtr<AsyncFromSyncIterator> create(Realm&, IteratorRecord sync_iterator_record);
static NonnullGCPtr<AsyncFromSyncIterator> create(Realm&, NonnullGCPtr<IteratorRecord> sync_iterator_record);
virtual ~AsyncFromSyncIterator() override = default;
@ -28,9 +28,9 @@ public:
IteratorRecord const& sync_iterator_record() const { return m_sync_iterator_record; }
private:
AsyncFromSyncIterator(Realm&, IteratorRecord sync_iterator_record);
AsyncFromSyncIterator(Realm&, NonnullGCPtr<IteratorRecord> sync_iterator_record);
IteratorRecord m_sync_iterator_record; // [[SyncIteratorRecord]]
NonnullGCPtr<IteratorRecord> m_sync_iterator_record; // [[SyncIteratorRecord]]
};
}